Ive nicked this for you sambo mate, came from maximum yield mag so its good info.
Chemical control should be considered a last resort. Chemicals should be sprayed only in veg or early flower to prevent absorption into the buds and burning bud hairs. Chemicals may have to be applied repeatedly to be effective, and may take a few days for noticeable results. Use a surfactant to help adhere chemical to leaf surface. Some chemicals are more harmful than others; follow label directions and observe precautions.
Always spot spray first. Spraying individual leaves can be an option.
Note: many chemicals will leave a residue that appears similar to powdery mildew!
* Alkaline water:
Alkaline water can affect powdery mildew, as mildew cannot grow in basic conditions. Mist plants generously with water at 8.0+ pH frequently; discontinue when buds begin to mature to prevent budrot.
[Editor's note: this does work and is effective in late flower. Alkaline water does not seem to affect buds or bud hairs. The effect is temporary, but drastically slows mildew grow and spread. Reapply every 4-5 days.]
Baking soda: Sodium Bicarbonate
"Sodium collapses the powdery mildew cell wall". Baking soda leaves an alkaline residue on the leaves, which should be washed off with water before more is applied.
Foliar spray: 15ml / gallon
Potassium Bicarbonate:
"Collapses and desiccates the mildew hyphae. Very safe, very effective contact fungicide". Kaligreen and Armicarb100.
Garden sulphur:
A common non-toxic spray, sulfur interferes with mildew cellular respiration. Spray young plants weekly before hairs form (or spray lower leaves only), then discontinue. Do not wash off. Note: dried sulphur spray looks similar to mildew. For best results, prune plants in veg/early flower, then spray lower stems and foliage. Warning: can give a sulphur taste if sprayed directly onto buds!
Foliar spray:
15-20ml sulphur powder/Liter water. Keep well mixed when spraying.
Note: will not wash off buds. Re-application may be necessary.
Neem Oil:
Protects and kills mildew by inhibiting respiration; also protects against mites and may improve plant vigor. Results are noticeable in a couple of days.
Pro-silica: (Soluble Silicon)
”… increases resistance to pathogens by accumulating in…(leaf and root) cells of plants, providing a barrier against penetration by invading fungi such as powdery mildew and Pythium. Foliar applications leave deposits of silicon…on the leaf surface that promote effective physical barriers to…infection.” Pro-silica is alkaline.
Foliar spray: 1 part in 5
SM90:
A natural plant extract in a vegetable oil base.
Foliar spray: 10ml/liter
Copper Sulphate:
"Copper ions inactivate some fungal enzyme systems, killing the mycellium."
Effective one-shot application, but production may be discontinued.
Benomyl: Apply in veg only.
Malatox:
by the chronic:
…”This is a wonder cure. Mildew completely vanishes for up to 7 weeks! Make sure you spray before the first week of flowering.”
Foliar spray: 2.5ml per liter of water.
Biological controls:
Unpasterized milk:
Note: must be fresh, not store bought (which is pasturized). Diltute 10 parts water to 1 part milk. Works, although the milk may smell.
AQ10:
A biofungicide. Ampelomyces quisqualis is a fungus that "parasites the powdery mildew organism. It offers control over a long period of time." Effective only in initial stages of infection.
Plant Shield:
Plant Shield is a foliar spray (General Hydroponics), which kills many types of leaf and root fungus. Trichoderma harzianum strain T-22. Safe to use. Takes 2-10 days.
Serenade:
"The fermentation product of a bacterium, bacillus subtillis, that inhibits cell growth of fungi and bacteria. It is effective and easy to spray or use as a dip". Contact fungicide.
